Protective covering for preventing accumulation of ice on airfoils



pm L 1947, E. E. HESTON PROTECTIVE COVERING FOR PREVENTING ACCUMULATION OF ICE ON AIRF'OILS Filed Nov. 15, 1945 XII).

Patented Apr. 1, 1947 PROTECTIVE COVERING FOR PREVENTING ACCUMULATIGN F ICE ON AIRFOILS Eugene E. Heston, Akron, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York Application November 13, 1945, Serial No. 628,163

15 Claims.

The invention relates to protective coverings for surfaces and especially to coverings for preventing the accumulation of ice edges of airfoils.

In prior constructions of protective coverings especially for airfoils such as wings and the like, in which a stretchable porti-on between a central inflatable tube Zone and an attaching margin has been subjected to stretch for removing ice from such portion upon the inflation of the tube or tubes in such zone, the acti-on of such coverings under Isome icing conditions of particular severity has not been effective to obtain full cleanliness of ice removal in the stretchable portion. Also, the rapidly repeated stretching of the stretchable portion rearward of the tubes has undersorne ice conditions tended to craze or merely crack the ice repeatedlir rather than break and remove it thoroughly from the surface of the covering.

The stretchable portions of such prior coverings have been generally of unreinforced resilientrubber sheet material or of resilient-rubber sheet material reinforced against tearing as by widely spaced-apart narrow strips of stretchable fabric such as Trico for isolating tears of the rubber covering between the strips, which latter arrangement has extensive areas of unreinforced rubber construction. For both 0f these arrangements, the ice may be cracked into pieces or Darticles by the stresses of the initial chordwise stretching of such portions, which pieces serve to stiften the resistance to stretching of the rubber thereunder because of their adhered relation to such rubber throughout their seated areas. In view of this condition, the stretching forces due to further stretching of such portions are not fully distributed and transmitted throughout the rubber immediately underlying such adhered pieces but rather are absorbed by a greater Istretching action of the rubber immediately adjacent the regions of the cracks by virtue of the inherent stretching characteristics of the rubber material. Thus once the ice-deposit is cracked, the tendency for both arrangements is to trans.- mit the stretching forces around an ice-particle rather than throughits seated area at the interface between the ice-particle and the covering, and both arrangements are relatively ineifective to reduce the adhered area between the covering and the ice-particle and to loosen the latter for removal by the flow of air.

Woven fabrics or knitted fabrics as reinforcements in the stretchable portions are ordinarily not such as to accomplish the purpose of the invention even though substantial stretchability on the leading 2 may be afforded by the twist of the threads or the particular weave of such fabrics. Such reinforcements unduly limit the extent of stretchability of the rubber material and permit stretching of the stretchable portions only in the direction of the stretching forces.

An object of the invention is to provide for stretching the surface of a protective covering in a manner effectively overcoming the foregoing and other difculties.

Other objects of the invention are to provide an improved loosening action of ice adhering to the covering; to provide for effective distribution of stretching action in the direction across a stretchable portion of the covering and throughout the stretchable portion along its extent; t0 provide for shifting movement of portions of the covering laterally of the direction of stretch and for compelling such movement by virtue of the aforesaid stretching to eiect an improved shearing action on ice adhering to the covering; to provide for such lateral shifting movement in opposite directions at zones of the covering, and to provide for simplicity of construction, convenience of manufacture and eiectveness of operation.

These and other objects and advantages of the invention will be apparent from the following description.

In the accompanying drawings which form a part of the specification and in which like numerals are employed to designate like parts throughout the same.

Fig. 1 is a perspective front View from. above of protective apparatus or coverings on the leading edge of an aircraft wing and constructed in accordance with and embodying the invention, parts being broken away.

Fig. 2 is a plan view from above of the protective covering before assembly with the wing, parts being broken away and in section.

Fig. 3 is a section taken along line 3-3 of Fig. 2, parts being broken away,

Fig. 4 is aview showing weftless sheet material having wavy cords mounted on a sheet base, parts being broken away, and

Fig. 5 is a sectional view likeFig. 3 but showing a modied construction of the covering, parts being broken away.

In the illustrative embodiment shown in Figs. `1 to 4 inclusive, protective coverings or apparatus I0, I 9a for preventing the accumulation of ice on the leading edge of an airfoil such, for example, as an aircraft wing I I may be mounted at the inboard and the outboard regions of such wing I l at the respective sides of an engine nacelle I2 having a propeller I3. The inboard and outboard protective coverings I and Illa are constructed substantially alike; hence only the outboard covering Il] will be described in detail.

The protectivecovering IIl includes a body I5 of elastic material such, for example, as resilient rubber, natural or synthetic, or plastic having a resilient character such as a rubbery plasticized polymer composed predominantly of vinyl chloride, or other resilient rubber-like material. The covering I0 which may be of elongated tapering form for smooth conformance to the leading edge ofthe airfoil includes an expansible or inflatable portion I6 intermediate spanwise-extending attaching margins I1, I8 and includes stretchable portions I9, 20 extending `rearwardly .from the expansible portion IB substantially to such margins I1, I8. The body I5, preferably of resilient rubber material, has at such expansible or inflatable portion I6 a plurality of inflatable tubes 2l, 22, and 23 extending spanwise in side-by-side relation, which inflatable tubes may have walls of suitable rubber material reinforced by extensible or substantially inextensible woven fabric material and which tubes upon inflation provide for chordwise-stretching of the strechable portions I9, 20.

To the end of promoting the desired distribution of stretching in the chordwise direction of the stretchable portions while at the same time compelling lateral or spanwise shifting movement of the outer surface of the covering at adjacent zones of such portions, the invention provides Yfilameritary material such as cords 24, 24 which are embedded in and may be adhered to the rubber body I5 adjacent and in the proximity of the outer face thereof and overlying the inflatable tubes 2| to 23, as shown especially in Fig. '2 and 3. The cords 24, 24 are arranged substantially individual and in a side-by-side butnon-straight and laterally devious disposition, preferably wavy as shown especially in Fig. 4, and extend desirably continuously chordwise ofthe covering between the attaching margins I1, I8. The respective opposite end-reaches of each of the cords are desirably `folded about suitable reinforcing beads 25, 26, which beads may be, lfor example, of suitable flat metal wire, and the .folded-over and overlapping arrangement assuresanchoring the cords.

The cords 24, .24 may be of cotton, linen, hemp, wool or other vegetable or animal fibers, or of silk, rayon .or nylon or other articallamentary materials, or of glass, metal, and .asbestos fibers; and such cords may have ya staple ber or ,continuous lament construction. The cords .or other filamentary elements are mounted for .substantially individual action in the rubber-like material, in .contrast to prior closely woven or knitted fabrics. This individual action may be obtained by arranging the cords or lamentary elements as a substantially Weftless fabric, that is, a fabric :without weft threads, or a few widely-spaced wefts, or the cords or ilamentary-elements even ,I

may have weak weft threads subject to subsequent `:breakage as in use..

The :cords 24, 24 as shown `especially Ain Fig. 4, extend in the chordwise direction positioned .closely adjacent and ralongside one another. Preferably, they are spaced-apart spanwise to fa-A 4 closely adjacent cords desirably lie in substantially a horizontal plane with relation to a face of the covering such that the waviness or deviousness of the cords is substantially confined to the lateral or spanwise direction of the covering as viewed from said face for facilitating compelling the desired shifting movement of the outer face of rubber material at adjacent Zones of the stretchable portions I9, 2G.

For facilitating the assembly of the cords with the other parts of the covering Iii, such cords 24, 24 may be adhesively secured in the desired wavy formation to a relatively thin sheet base 21 of suitable rubber material, as shown especially in Fig, 4l, which wavy formation provides adjacent zones of waves in general alignment to one another, the zones extending spanwise. Such adhesive attachment to the base 21 facilitates positioning and maintaining the cords in the desired aligned and wavy formation at the stretchable portions and overlying the inflatable tubes but beneath and in the proximity of the outer face of the covering Il! during the assembly of the various parts comprising the covering. The fabric, cords, and rubber parts of the covering are preferably uni-ted integrally as by vulcanization under heat and pressure.

Under the inflating action of the tubes which may be suitably connected to a source of air under pressure in the wing structure, for example, the stretchable portions I9, 2li move outwardly away from the surface of the wing and are stretched in the chordwise direction to a substantial extent for breaking and loosening the ice at such portions. Such stretching action across the `stretcnable portions I9, 20 tends to straighten the wavy cords, each cord tending to assume a straightened condition along the neutral axis of the waves. By virtue of their relatively close positioning to the outer1 face of the covering and their non-straight and laterally devious disposition within such covering, the cords promote distribution of the stretching action of the rubber material at the outer face of the portions I9, 20 throughout the extent of such portions as governed by the cords, .and such movement of the .cords toward the straightened condition compels spanwisemovement of adjacent waves of each cord in opposite spanwise directions, which `in turn effects lateral shifting movement of the outer face of rubber material immediately overlying the zones of, waves. The lateral shifting movement of adjacent Zones of waves of the cords in such opposite directions is indicated in Fig. 4 by arrows at 28, 29, 30, 3l.

Because of the relatively close spanwise-positioning and the wavy disposition of the cords 24, l24 throughout the extent of the stretchable portions IS, 2B, such cords promote and govern the distribution of chordwise stretching action at the outer face of the covering at such portions and assure compelling spanwise movement of such outer face in opposite directions at adjacent zones of waves extending spanwise throughout the stretchable portions. In this manner, an improved ice-shearing action at the stretc'hable portions is obtained since the stretching forces are transmitted not only around an ice-particle but also effectively through the seat thereof thereby reducing the adhered area at the interface between the covering and the ice-particle and 'loosening the latter for prompt removal by the 4ambient flo-w of air thereover.

In the operation of the covering IB, the 'in- 'atable tubes 2I22 and 23 may be inflated simultaneously or sequentially, but preferably lare inflated in alternatiton such, for example, that the inner tube 22 is inated rst and the outer tubes 2|, 23 vare inated simultaneously and subsequently. For such an inflation cycle, the iniiation of the inner tube 22 causes little or no stretching of the stretchable portions I9, 29, a1- though the covering immediately over such tube is expanded or distended which may effect some straightening of the overlying cords at the immediate region of the inner tube 22 and such straightening of the cords 24, 24 further facilitates the breaking and loosening of the ice deposited thereon. The simultaneous inflation of the outer tubes 2 I, 23 not only breaks and loosens the ice deposited over such outer tubes, but in addition moves the stretchable portions i9, 20 outwardly away from the wing and stretches such portions in the chorclwise direction.

Such chordwise-stretching of the stretchable portions I9, 29 causes the desired straightening action of the cords 24, 24 throughout the extent of the stretchable portions promoting the distribution of stretching action of the rubber material at the outer face of the covering in the chordwise direction as governed by the cords and also causes the movement of the cords toward the straightened condition which compels lateral shifting movement of adjacent spanwise-extending Zones of such outer face overlying the Zones of waves. The ice deposited thereon is broken and loosened effectively by virtue lof such improved ice-shearing action such that the scavenging action of the flow of air removes promptly the broken pieces of ice whether such pieces be relatively large or small in size. As discussed hereinabove, the distribution of chordwise stretching and the lateral shifting movement at adjacent zones of the covering makes possible the improved ice-shearing action, whereby the adhered area of each broken piece of ice is reduced and is relatively small facilitating prompt and thorough removal of such ice from the covering and eiectively prevents merely crazing or cracking the ice repeatedly as in prior constructions. l

In the modied construction 34 of the covering shown especially in Fig. 5, cords 35, 35 of suitable material are arranged substantially like the cords 24, 24 but the cords 35, 35 are discontinuous over the expansible or inatable portion of the covering having tubes 39, 49. The cords `35, 35 having the desired side-by-side wavy disposition are embedded within a suitable rubber body 36 adjacent the outer face thereof and only in the stretchable portions of the covering. Each of the cords 35, 35 are desirably anchored like the cords 24, 24 about a suitable metal bead 31, 31 at each `attaching margin 38, 38 and the inner endreaches of the cords 35, 35 terminate at the outer margins of the outer iniatable tubes 39, 39. Suitable tapes 4 I, 42 mounted in overlapping relation with such end-reaches at the opposite faces of the layers of cords 35, 35 and with the outer marginal portions of the tubes 39 39 are united with such cords and tubes as by an adhesive such, for example, as rubber cement and assure anchoring the cords to the respective outer tubes 39, 39 thereby facilitating the straightening action of the cords 35, 35 upon inflation of the tubes eecting chordwise-stretching of the stretchable portions of the covering 34. The operationcf the covering 34 is substantially like that of the covering Ii! with respect to the improved ice-shearing action at the rearward stretchable portions.

The. fabric, cord, andrubber parts of the `coverin'gs I0, lila and 34 are preferably united as by vulcanization under heat and pressure thereby providing an integral and unitary construction facilitating mounting of the coverings at the leading edges of the wing. The attaching margins of the coverings may be recessed, if desired, for receiving fairing strips 44, 44 to promote the smooth iiow of air across the covering and promote the maintenance of the desired aerodynamic characteristics of the wing or other airfoil.

Variations may be made without departing from the scope of the invention as it is defined by the following claims.

I claim:

1. Apparatus for preventing the accumulation of ice on a surface, said apparatus comprising-a covering for said surface having a portion of resilient rubber-like material between opposite margins of the covering, and means for stretching said portion in the direction toward said margins, said portion having a plurality of' elements of lamentary material united with said rubberlike material and extending generally in saiddirection, said elements being substantially individual and arranged in side-by-side but nonstraight disposition with the elements laterally devious as viewed from a face of the covering so that the tendency of said elements to straighten from their non-straight arrangement under stretch of said portion in said direction promotes distribution of the stretching action of said rubber-like material throughout said portion as governed by said elements, and shifting of portions of said covering laterally of said direction of stretch as viewed from sadface of the covering is compelled by the movement of the non-straight elements toward the straightened condition under the stretching of said portion of the covering.

2.. Apparatus for preventing the accumulation of ice on a surface, said apparatus comprising a covering for said surface having a portion of resilient rubber-like material between opposite margins of the covering, and means for stretching said portion in the direction toward said margins, said portion having a plurality of elements of lamentary material embedded in said rubberlike material beneath the outer face of the covering but in proximity to said face and extending generally in said direction, said elements being substantially individual and larranged in sideby-sde but non-straight disposition with the elements laterally devious as viewed from said outer face oi the covering so that the tendency of said elements to straighten from their non-straight arrangement under stretch of said portion in said direction promotes distribution of the stretching action of said rubber-like material throughout said portion as governed bysaid elements, and shifting of portions of the outer face of said rubber-like materia-l at said portion of the covering laterally of said direction of stretch as viewed from said outer face is compelled by the movement of the non-straight elements toward the straightened condition under the stretching of said portion of the covering.

3. Apparatus for preventing the accumulation of ice on a surface, said apparatus comprising a covering for said surface having a portion of resilient rubber-like material between opposite margins of the covering, and means for stretching said portion in the direction of said margins, said portion having a plurality of elements of iilamentary material united with said rubber-'like material and extending generally in said direction, said elements being substantially individual V7 uand arranged :ln side-by-side `wavy disposition with waves of adjacent elements in general alignment with one another in zones laterally of said direction as viewed from a, face of the covering so that the tendency of said elements to straighten from their wavy arrangement under stretch of said portion in said direction promotes distribution of the stretching action of said rubber-like material throughout said portion as governed by said elements, and shifting of said zones of the covering in opposite directions laterally of said directio-n of stretch as viewed from said face Aof the covering is compelled by the movement of the wavy elements toward the straightened condition under the stretching of said portion of the covering.

4. .Apparatus for preventing the accumulation of ice on a surface, said apparatus comprising a covering of resilient rubber-like material for said surface, said covering comprising an expansible portion intermediate opposite margins of the covering including an iniiatable passage beneath the outer face of the covering at said portion and said covering comprising a stretchable `portion of said rubber-like material between said expansible portion and one of said margins, and means for innating said passage to distend said expansible portion and to stretch said stretchable portion in the direction toward said margins, said stretchable portion having a plurality of elements of llamentary material united with said rubberlike material and extending generally in said direction, said elements being substantially individual and arranged in side-'by-side but nonstraight disposition with the elements laterallfs7 devious as viewed from said outer face of the covering so that the tendency of said elements to straightenfrom their non-straight arrangement under stretch of said stretchable portion in said direction upon iniiation of said passage promotes distribution of the stretching action of said rubber-like material throughout said stretchable portion as governed by said elements, and shifting of portions of said stretchable portion laterally of said direction of stretch as viewed from said outer face of the covering is compelled by the movement of the non-straight elements toward the straightened condition under stretching of said stretchable portion.

5. Apparatus as dened in claim 4 in which said elements of lamentary material are embedded in the rubber-like material of said stretchable portion and beneath the outer face thereof but in proximity thereto so that shifting of said elements toward `their straightened condition compels shifting of said rubber-like material at the outer face of said portion.

6. Apparatus as defined in claim 4 in which said elements of lamentary material are arranged in wavy disposition with waves of adjacent elements in general alignment with one another in zones laterally of. said direction as viewedffrom a face of the covering so that shifting of said zones of the covering in opposite directions laterally of said direction of stretch as viewed from said face of the covering is compelled by the movement of the wavy elements toward the straightened condition under stretching of said stretchable portion.

7. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering for said leading edge having a portion of resilient rubber-like material between margins of the covering spacedapartV in the chordwisey direction of the covering,

and `meansV for stretching said portion-in 4said chordwise direction, said portion havinga plurality of elements of i'llamentary material united with said rubber-like material and extending generally in said chordwise direction, said elements being substantially individual and arranged in side-by-side but non-straight dispositionwith the elements deviating in the spanwise direction as viewed from a face of the covering so that the tendency of said elements to straighten from their non-straight arrangement under chordwise stretch of said portion promotes distribution of the stretching action of said rubber-like material throughout said portionas governed by said elements, and shifting of portions of said covering in said spanwise direction as viewed from said face of the covering is compelled by the movement of the non-straight elements toward the straightened condition under the chordwise stretching of said portion ofthe covering.

8. Apparatus forpreventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering for said leading edge having a portion of resilient rubber-like material between margins of the covering spacedapart in the chordwise direction of the covering, and means for stretching said portion in said chordwise direction, said portion having a plurality of elements of iilamentary material embedded in said rubber-like material beneath the outer face of the covering but in proximity to said face and extending generally in said chordwise direction, said elements being substantially individual and arranged in side-by-side but vnonstraight disposition with the elements deviating in the spanwise direction as viewed from said outer :face of the covering so that the tendency of said elements to straighten from their nonstraight arrangement under chordwise `stretch of said portion promotes ldistribution Vof the stretching action of said rubber-like material throughout said portion as governed by said elements, and shifting of portions of the .outer face of said rubber-like material at saidportion of the covering in said spanwise direction as viewed from said outer face is compelled by the movement of the non-straight elements toward the straightened condition under the chordwise stretching of said portion of the covering. v

9. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering for said leading edge having a portion of resilient rubber-like material-between margins of the covering spacedapart in the chordwise direction of the covering, and means for stretching said portion in said chordwise direction, said portion having a plurality of elements of lamentary material united with said rubber-like material and extending generally in saidchordwise direction, said elements being substantially individual and arranged in. side-by-side wavy disposition with waves lof adjacent elements in general alignment with 'straightened condition under chordwise stretching of said portion of the covering.

10. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering of resilient rubber-like material for said leading edge having margins of the covering spaced-apart in the chordwise direction of the covering, said covering comprising an inflatable portion intermediate said margins including an inflatable tubular passage extending spanwise beneath the outer face of the covering at said portion and said covering comprising a stretchable portion of said rubberlike material between said expansible portion and one of said margins, and means for inating said passage to distend said inliatable portion and to stretch said stretchable portion in the chordwise direction, said stretchable portion having a plurality of elements of lamentary material united with said rubber-like material and extending generally in said chordwise direction, said elements being substantially individual and arranged in side-by-side but non-straight disposition with the elements deviating in the spanwise direction as viewed from said outer face of the covering so that the tendency of said elements to straighten from their non-straight arrangement under chordwise stretch of said stretchable portion upon inflation of said passage promotes distribution of the stretching action of said rubber-like material throughout said stretchable portion as governed by said elements, and shifting of portions of said stretchable portion in said spanwise direction as viewed from said outer face of the covering is compelled by the movement of the non-straight elements toward the straightened condition under chordwise stretching of said stretchable portion.

11. Apparatus as dened in claim in which said elements of laznentary material are embedded in the rubber-like material of said stretchable portion beneath the outer face thereof but in proximity thereto so that shifting of said elements toward their straightened condition compels shifting of said rubber-like material at the outer face of said stretchable portion.

l2. Apparatus as defined in claim l0 in which said elements of nlamentary material have opposite end-reaches thereof anchored at one of said margins and at said inatable portion, and in which said elements are embedded in the rubberlike material of said stretchable portion beneath the outer face thereof but in proximity thereto so that shifting of said elements toward their straightened condition compels shifting of said rubber-like material at the outer face of said stretchable portion.

13. Apparatus as dened in claim 10 in Which the non-straight elements of fllamentary material are embedded in the rubber-like material of said covering at said stretchable portion and continuously across said inflatable portion.

le. Apparatus as dened in claim 10 in which said elements of lamentary material are arranged in wavy disposition with waves of adjacent elements in general alignment with one another in zones in the spanwise direction as viewed from said outer face of the covering so that shifting of said zones of the covering in opposite spanwise directions as viewed from said outer face of the covering is compelled by the movement of the wavy elements toward the straightened condition under chordwise stretching of said stretchable portion.

15. Apparatus as defined in claim 10 in which said elements of lamentary material are embedded in the rubber-like material of said covering at said stretchable portion and continuously across said inatable portion beneath the outer face of said covering but in proximity thereto, and in which said elements are arranged in wavy disposition with waves of adjacent elements in general alignment with one another in zones in the spanwise direction as viewed from said outer face of the covering so that shifting of the wavy elements toward their straightened condition compels shifting of said rubber-like material at the outer face of said stretchable portion in opposite spanwise directions at said zones under chordwise stretching of said stretchable portion.

EUGENE E. HESTON, 

